1. Field of the Invention
The present invention relates to a tapping machine for performing a tapping operation on a workpiece in plate form, and, more specifically, to a tapping machine wherein, after a tapping hole is formed or a deforming or plunging operation is performed on a workpiece, the tapping machine carries out the tapping operation continuously.
2. Description of the Prior Art
When a thin workpiece is to be worked or tapped, it is necessary to deform the workpiece at the spot to be tapped in order to make the material of the spot thick so that the number of threads to be formed on an inner wall of the tapping hole may be increased, thereby obtaining a firm connection between the tapping hole and bolt threaded therein. Such an operation is known as a deforming or plunging operation.
Conventionally, in performing a tapping operation on a plate workpiece, a system is commonly used by which the forming of the tapping hole or the deforming or plunging operation is first performed by means of a punch press, after which the workpiece is moved to the tapping machine and the tapping is performed while the workpiece is being positioned manually. Accordingly, the processing efficiency is poor in such a conventional operation, and there is the problem that part of the operation is unnecessary.
Accordingly, the configuration is being developed by which the tapping unit is attached to the punch press to perform the tapping operation continuously after the forming of the tapping hole or the deforming or plunging operation is carried out. As examples of configurations by which the tapping unit is attached to the punch press, there is the configuration by which the driving source of the ram on the punch press drives the tapping unit, and the configuration by which a tapping unit provided with its own drive source is attached to the punch press.
In the configuration in which the driving source of the ram on the punch press drives the tapping unit, the control of the rotational linkage and vertical movement of the taps is extremely difficult because the rotation and vertical movement of the taps on the tap unit originate from the vertical movement of the punch press ram. Because it is difficult to interrupt the linkage of the vertical movement of the punch press ram with the rotation etc. of the taps on the tapping unit, when a plurality of tapping units is provided, these tapping units all operate simultaneously. Accordingly, it is difficult to provide tapping units with taps of different diameters. In addition, in the case where the pitch and diameter of the taps is changed, there is the problem that the operation to make this change can be extremely dangerous.
In the configuration in which a tapping unit provided with its own drive source is attached to the punch press, when a plurality of tap types is used in performing the tapping operation, it is necessary to have a tapping unit for each size of tap, which results in high cost. In addition, because each tapping unit is provided with its own drive source, each tapping unit is large in size, and the problem arises that the space for accomodating the punch press must be very large.